1. Field of Invention
The present invention relates to heating systems in general and a waste oil fire heater systems for heating ambient air by the combustion of waste oil and other materials in particular.
2. Discussion of Prior Art
The use of waste oil as a fuel source in heating systems is well known. See "Heat Exchanger" issued to James C. Wilson as U.S. Pat. 4,905,661 on Mar. 6, 1990 and "Coaxial Dual Primary Heat Exchanger" issued to James C. Wilson as U.S. Pat. 5,022,379 on Jun. 11, 1991.
Waste oil heating systems typically utilize lubricating oil which is removed from vehicle engines and other devices requiring such lubrication. This waste oil contains a number of contaminants from the engines in which they were used including unburned fuel products from such engines, minor portions of metal from wear in such engines, compounds for the control of viscosity and other contaminants (at least as far as clean combustion is concerned). When this waste oil is burned, even in the best burners, there are by-products of such combustion, such as ash or mineral deposits, which collect on the burner chamber walls.
This accumulated material, when located on the burner chamber walls acts as an insulator between the very hot combustion gases and the cooler combustion chamber walls. If, as is desirable in most oil fired heaters, the combustion chamber wall serves to convey heat to the ambient air to be heated, the accumulation of ash acting as an insulator reduces the heat transfer from the combustion gases to the ambient air to be heated and accordingly reduces the efficiency of the heat exchanger. Thus it is desirable to avoid or reduce the ash accumulation on such walls to the extent possible.
If the combustion chamber walls are permitted to rise to very high temperatures, the localized expansion of the metal may cause warping and/or other defects in the combustion chamber. Repeated heating and cooling cycles may in turn lead to high stresses and/or fracturing of the chamber walls over long periods of operation. A reduction in the wall temperatures of the combustion chambers in waste oil fired heater would tend to reduce these adverse effects.
Furthermore, high localized temperatures in the combustion chamber walls permit and encourage corrosion and/or oxidation of the walls. This can lead to early failure and/or burn through of the chamber walls.
Accordingly, in view of the above, there is a continuing problem with existing oil fired furnaces in that ash accumulation reduces the efficiency of heat transfer and high temperatures cause expansion and consequence stress in the combustion chamber as well as possible corrosion and/or oxidation of the chamber walls.